1. Field of the Invention
The present invention relates generally to a two-axis joint assembly and, in one more particular embodiment, provides a low profile, compact, surface-mountable assembly which supports high side loads with low friction operation.
2. Description of Related Art
A two-axis joint is a mechanical device which provides two degrees of freedom of motion between connected components, e.g., a joint between a base and a rod such that the rod is constrained to move only within a first axis of rotation and/or a second axis of rotation.
A simple example of a commonly used two-axis joint is a two-axis connection for oars in a row boat. A yoke or shackle or clevis provides the receptacles or base into which the oars are placed. The oars fit into the U-shaped yokes and, in this example, may also be pinned in position or least prevented by friction from sliding whereby the oars can swing up and down to provide the first axis of rotation for rotational movement of the oars. The U-shaped clevis or yoke has a shaft at the end of the U-shaped clevis or yoke which extends through a socket or perhaps through aligned holes in several flanges. The shaft is rotatable in the socket or holes through which it extends to provide the second axis rotation such that the oars rotate around the shaft and clevis to swing back and forth. Accordingly, once the oars are positioned in the yoke or clevis, the oars may be pivoted upwardly and downwardly and also rotate around the joint. The clevis is secured in position by the shaft to thereby act as a fulcrum so that side loads applied thereto are transferred to the water so as to propel the boat. The length and diameter of the shaft and construction of the socket is designed to be sufficiently long and mechanically strong to absorb the side loads applied during rowing.
Conventional high moment two-axis joints require increased depth of engagement between the rotating shaft and a housing to which the shaft is secured to react to an increase in applied moments. This type of configuration requires the depth of engagement to act as a reacting or bearing surface below the joint to react to the applied moments. In other words, a long shaft has to be inserted into a deep hole to react to the moments created by side loads applied at one end of the shaft. The deeper the hole is, the more space required for mounting the device. However, in some applications where a two-axis joint would be highly desirable, a mounting structure which provides a deep hole or support therefore may be unavailable or undesirable.
It will be understood that the example of the two axis connection for oars in a row boat is illustrative of a relatively low-load application which may not utilize bearings. To support very high moments acting thereon, conventional two-axis joints may utilize bearings axially spaced relatively far apart along the shaft to meet the high moment requirements. Because of the shaft length, these conventional two-axis joints assemblies are not suitable for applications where only minimal intrusion is allowed onto the support platform. The shaft-in-hole approach requires that space below the joint be available to react the moments. This space is not available for applications requiring a surface mounted only apparatus.
U.S. Pat. No. 6,290,182, issued Sep. 18, 2001, to Grunditz, discloses a joint in a space vehicle to hold together a first part of the vehicle and a second part of the vehicle that can be separated from the first part, in which the joint includes a first flange member attached to the first part of the vehicle and a second flange member attached to the second part of the vehicle. A number of clamps equipped with two clamping lips are distributed around the perimeter of the flange members that transfer radial force from a tensioning means, arranged around the clamps, to both of the flange members in order to press these together, whereby rolling members are arranged between at least one of the clamping lips of the respective clamps and the adjacent first or second flange member.
U.S. Pat. No. 6,418,811, issued Jul. 16, 2002, to Rosheim, discloses a controlled relative motion system comprising a base support, a manipulable support, a group of link end constrainers each having a first portion movably connected to a second portion thereof so that ends of the first and second portions can be selectively separated from one another in a selected direction so as to have a selected distance therebetween, and two groups of pivoting links. With at least four link end constrainers in the group thereof, the first group of pivoting links has corresponding links each rotatably coupled to force imparting means or to the base support so as to be rotatable about a corresponding base link axis where each of said base link axes extend into regions between adjacent ones of said first group of pivoting links into which regions said base link axes of said adjacent ones also extend, and each coupled to a first portion end of a corresponding one of the group of link end constrainers. The second group of pivoting links each rotatably coupled to the manipulable support and a corresponding one of the group of link end constrainers second end. Four or more or less numbers of link end con strainers in the group thereof are useable in the form of straps or interconnected “eye” bolts with corresponding number of pivoting links in the two groups.
U.S. Pat. No. 6,494,407, issued Dec. 17, 2002, to Arulf, discloses a joint on a spacecraft for holding together a first craft part and a second craft part, detachable from the first craft part. The joint comprises a first flange fixed on the first craft part, and a second flange fixed on the second craft part, and a number of clamps having a first and a second clamp lip, the said clamps being distributed about the periphery of the flanges. The clamps transfer radial forces from a tightening device, fitted to the clamps, so as to fasten the two flanges together. The first flange is clamped between a first clamp surface on the first clamp lip, and a separation surface on the second flange. These surfaces form an acute angle the apex of which is directed in towards the spacecraft.
U.S. Pat. No. 6,612,101, issued Sep. 2, 2003, to Dillon, discloses a method for articulating an articulated vehicle from a rest position, the vehicle being composed of a forward unit and a tracked rearward unit having a pair of powered tracks. The forward and rearward units are connected by a joint and an articulation cylinder. The method powers up only one track, while simultaneously actuating the articulation cylinder.
U.S. Pat. No. 6,658,962, issued Dec. 9, 2003, to Rosheim, discloses a controlled relative motion system having first and second support structures with a controlled output position joint connecting them, and with similar joints on these support structures. One joint is coupled to another controlled relative motion system having an output carrier rotatable in two perpendicular directions through the use of gears therein. This output carrier supports two articulated manipulating systems of which one has a single axis rotatable subbase supporting a rotatable gripping extension, and the other has a shackle connected to a base effector which shackle is supported on a fixed pedestal and another shackle connected to a base effector which shackle is supported on a moveable pedestal.
The above cited references do not disclose a low-profile surface mountable two-axis joint capable of supporting high side loads and operating with little friction. In related art, a two-axis joint generally consists of two pairs of ball bearings in an orthogonal configuration. Each pair of bearings require a spatial separation distance to provide moment reaction capability. However, two orthogonal ball-bearing sets require significant volume. When reduction of bending moment due to external loads is desired, the joint generally needs to penetrate the mounting surface of the applicable structure or platform to lower the point of application of applied forces. The problem is that, as a result of previous statement, the joint is partially embedded in the applicable structure or platform. Those skilled in the art have long sought and will appreciate the present invention that addresses these and other problems.